The present invention relates to presses used to flatten dough-like material, for example edible dough materials used in tortillas, pizzas and similar food items.
Presses for dough material are well known and one type comprises a stationary press in which individual dough pieces are placed under a vertically movable platen, the platen compresses and spreads out the dough and then the platen is moved away revealing a flattened dough piece which must be manually removed. Another type is an automated dough press which typically comprises a moving belt and a vertically reciprocating platen. Generally the belt is stopped, and while stopped the platen, moves downwardly to engage and flatten a dough piece against the belt and then the platen moves upwardly. Subsequently the belt indexes to the next position to present a new series of dough pieces to the platen. While such an operation greatly increases the speed at which the dough pieces can be flattened into disks, such as tortillas and pizza crusts, the intermittent movement of the belt places a restriction on the speed at which the overall operation can be carried out, and the starting and stopping of the belt causes other difficulties relating to timing, energy requirements, wear and tear on the equipment as well as movement of the dough pieces relative to the belt.
A third approach to flattening dough pieces utilizes a continuously moving belt carrying the dough pieces and a roller positioned above the belt which engages and rolls out the dough onto the moving belt. While this arrangement allows for continuous movement of the belt, and so avoids the problems associated with intermittent operation of the belt, this approach creates its own problems, for example, the resulting dough pieces typically are not circular, but rather are oblong in shape, which are not as aesthetically pleasing for tortillas and pizzas. A raised rim, such as is used in pizza crusts, cannot be formed with this method and the dough itself responds differently when it is rolled out, as opposed to being pressed, which can affect the subsequent cooking of the dough. Finally, while the dough piece is being rolled out, the contact time between the roller and the dough itself is very brief which prevents the use of heat to condition the dough as it is being flattened, thus requiring an additional step if heat is to be applied.
A fourth approach to flattening dough pieces utilizes a continuously moving belt for receiving and carrying the dough pieces into the press area and from the press area to a point of further utilization. Vertically reciprocating platens are used to press the dough pieces into flattened shapes and the platens can be heated so as to provide heat into the dough product.
To allow both a vertically reciprocating platen and a continuously moving belt, the platens themselves are horizontally reciprocating such that as they move together and press the dough pieces onto the belt, the platens will be moving in the same direction and at the same speed as the belt itself. When the step of pressing, and optionally heating, is completed, the platens will move away from the belt and will be moved linearly backwards relative to the motion of the belt to be in position over a new set of dough pieces to be flattened. At this point the platens will reverse direction again and will accelerate up to the same speed in the same direction as the belt while the pressing occurs again.
Such an arrangement is shown in U.S. Pat. Nos. 4,938,126 and 5,006,358, both to Rubio, et al. In this parent and division patent there is disclosed a reciprocating press for making tortillas from dough balls in which various of the moving components are mechanically “slaved” to the press drive to control the timing of their respective actions. That is, the reciprocation movement of the press is controlled through a crank arm, cam and follower arrangement driven by the belt motor. The arrangement for controlling the speed of the feed mechanism is not disclosed.
U.S. Pat. No. 5,388,503 to Berkel discloses a reciprocating press for forming tortillas from dough balls in which the reciprocating movement of the press is achieved by a direct mechanical linkage to the drive for the conveyor belt. No feeding mechanism is disclosed for loading the dough balls onto the moving press belt.